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Sorry, gang, I should have been more specific. I am building (very slowly) a 601XLB. Since this discussion is in the General section rather than model specific I should have mentioned that.
My weight discussion was based on the parts for that plane and also based on my memory of checking the relative weights quite a few years ago. Assuming my memory is correct (and I am in my 70's now so who knows....) the difference between the Zenith and Grove gear for the 601XL almost cut the weight of the gear in half.
So, to condition my earlier response, weight savings remark is based on an old memory and is specific to the 601XL. The rest I stand by - stronger alloy, optional gun drilled internal brake lines, less metal, be careful of messing with the heat treating, etc.
Hi Bob: Not a problem, my only concern is that when I publish something I try and do my best to have that information be as accurate as possible since it stays out there virtually forever and later is being mis-quoted as fact.
Grove quotes the 601 gear at 32.2 pounds which is pretty much in line with the rest of the Zenith to Grove comparrison. I do agree with you on stronger alloy and optional gun drilling although this has the possibility of adding stress areas which could potentially lead to cracking (unlikly but possible). I personally would not powder coat the gear, not because of changing the temper which is in the 500 degree area and powder can be fully cured in the 350 degree range if you choose your powder carefully, but because the flexing of the gear has the potential to crack the powder.
As a plans builder I looked into building my own gear and the price of the gear from Zenair was $500. The raw material would have been about $300 plus whatever I had to come up with to make the bends. In the end I just bought the gear from Zenair.
They have a video of the gear being drop tested which shows how much it can bend and return to shape along with how much energy it will absorb. My concern with making the gear out of 7075 is how much of that energy will be transmitted to the air frame with the stiffer gear. I don't know about how every one else is but not all of my landings are as smooth as they should be. I don't want to be replacing metal that has been buckled from a landing that would have been absorbed with the 6061 gear.
Just my thought.